Sterile environment for additive manufacturing

ABSTRACT

In sterile, additive manufacturing wherein one lamella is successively built upon an underlying lamella until an object is completed, a sterile manufacturing environment is provided. A major chamber large enough to accommodate the manufactured object has sterile accordion pleated sidewalls and a sterile top closed with flap valves. A minor chamber for supporting the nozzles positioned above the major chamber has similar valves in corresponding positions. Nozzles for material deposition penetrate the pair of valves to block air and particles from entry into the major chamber where the nozzles make layer by layer deposition of the object using XY areawise nozzle motion relative to the object as well as Z nozzle vertical motion with the major chamber expanding as the object is formed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of pending U.S. patent application Ser.No. 14/614,952 filed Feb. 5, 2015 which claims priority from provisionalapplication Ser. No. 61/935,844, filed Feb. 5, 2014, now U.S. patentSer. No. 10/000,009 issued Jun. 19, 2018, for an invention entitledSTERILE ENVIRONMENT FOR ADDITIVE MANUFACTURING.

TECHNICAL FIELD

The invention relates to sterile 3-D manufacturing using layering of 2-Dlamellas.

BACKGROUND

Due to increasing popularity and significant technological developmentsin the field of additive manufacturing, it has become critical todevelop an efficient, sterile, and disposable chamber for 3D printing.As physicians, manufacturing professionals, and individuals make morecommon use of 3D printing systems, there will be a need to print manydifferent types of materials, including tissue, in a sterile chamberwhich can simply and rapidly be exchanged to allow for printing ofdiverse materials. An article in New York Times, Jan. 27, 2015 entitled“The Operation Before the Operation”, p. D6, describes a need foranatomical models for medicine and the use of 3D printed models.

The need for making anatomical models and actual body parts by additivemanufacturing was realized many years ago. The state of the art in thisfield several years ago was summarized in an article entitled “Rapidprototyping techniques for anatomical modeling in medicine” by M. McGurket al. in Ann. R. Coll. Surg. Engl. 1997; 79; 169-174 wherein 3-Dprinting of models was described. Models were created by spraying liquidthrough ink jet printer nozzles on a layer of precursor powder, creatinga solid thin slice. The printing process was repeated for eachsubsequent slice until the object was completed as a “green-state” partthat was then fired in a furnace to sinter it. The resulting object wasthen further treated to make a full density part.

In recent years the development of software for computer controlledrobotic X-Y motion systems used in the semiconductor and opticsindustries has made 3D printing of large objects easier than in formeryears. Software programs such as SolidWorks, AutoCad 360, and similarsoftware programs make layered construction of 3D objects a relativelylow cost and fast task for 3D printing equipment.

To achieve 3D printing of larger objects, print nozzles are directed inthe X-Y plane either by placing the object to be made on an X-Y tablewherein motion is provided below the nozzles, or mounting rails abovethe nozzles for X-Y motion directed from above the nozzles. An exampleof an X-Y table for motion below the nozzles is shown in U.S. Pat. No.5,760,500 to T. Kondo et al. wherein linear actuators or stepper motorsprovide independent motion to a table over the X-Y plane. Highlyaccurate stepper motors for this purpose are described in U.S. Pat. No.7,518,270 to R. Badgerow and T. Lin. A 3-D printer with overhead controlof nozzles is described in U.S. Pat. No. 5,740,051 to R. Sanders et al.

In either motion situation, the nozzles move in the X-Y plane relativeto the printed object and also move up in the Z plane starting from alower level and proceeding upwardly. A layer or lamella is first printedat a low level and then the next layer up is printed and so on until themodel or object is completed. Sometimes two nozzles are used, includinga first nozzle to spray or extrude a manufacturing material, such as apolymer, and a second nozzle to spray a support fluid for themanufacturing material, which may be soft or viscous. An example of asupport fluid may be an ink jet sprayed, ultra violet light cured resin.When the manufacturing material hardens, the faster drying support fluidis dissolved out. The use of chamber or accordion pleated sleeves inglovebox environments is known from U.S. Pat. No. 3,456,812 to J.Gandolfo et al.

Currently, many researchers, industry professionals, and individuals arelooking to additive manufacturing by 3D printing as the future of custommanufacturing of everything from organs to food products. Additivemanufacturing provides the flexibility to produce diverse items veryrapidly and at much lower cost than many previous manufacturingmethodologies. In particular, additive manufacturing technology by 3Dprinting techniques for patient-specific and potentially patient-derivedtissue and bone using tissue and stem cells. An object of the inventionwas to develop a sterile manufacturing environment compatible for 3Dprinting equipment that could be used for biological objectmanufacturing, as well as the validation of effective post-manufacturingsterilization of the manufacturing equipment.

SUMMARY

The above object has been achieved with a disposable, sterileenvironment additive manufacturing chamber that includes a rigidbaseplate with suction or self-adhesive bottom to adhere to the 3Dprinter base. Relative motion of the printheads with respect to thebaseplate is provided during manufacturing, with deflection withoutdimensional variations. The sterile environment is provided by flexible,accordion-type sides in a major chamber which is sterile on the insideand sealed to the baseplate. The sidewall construction resembles apleated Chinese lantern. The sidewall construction involves some portionthat has qualities of tough filter paper, such as Tyvek, and the rest ofwhich could optionally be transparent or opaque Mylar or nylon or otherplastic or paper combination. Tyvek is a registered trademark of theDuPont Company for non-directional, non-woven, high density polyethyleneor olefin fibers of diameter in the range of 0.5 to 10 micrometers,bonded together by heat and pressure without binders. The resultantmajor chamber structure is attached to the baseplate and can bestretched in the x, y, z coordinates as the printing heads move duringprinting. A flexible, stretchable lid is sealed to the sides to closethe chamber.

A minor chamber is removably fastened to the lid of the major chamber.The minor chamber provides support for the printheads. The minor chamberencloses a printhead support block and need not be much larger thanneeded for the support block. Both chambers have spatially separatedflap valves that are openable at a central print nozzle entry. The setof flap valves are openable one at a time when nozzles penetrate anopening so that air or particles cannot directly enter the major chamberwhere 3D printing will occur, similar to double doors in a buildingblocking wind from entry or airlocks on a ship. The lid has 3 or moreremovable attachment tabs that join the major and minor chambers. Themajor chamber has sidewall guide straps to keep the lid and sidewall ofthe major chamber from touching or dragging over the object beingmanufactured as well as a central attachment port for the manufacturinghead to be attached. Quick-detachable and disposable manufacturing headsubassemblies and nozzles attach to the non-disposable manufacturingheads of the 3D printer. The heads may include an extrusion head, nozzleand feeders or a sputter/spray jet and nozzle which may contact thematerial being printed. These parts are disposed after each use.

In summary, a pair of chambers provides a sterile environment for 3Dprinting of lamellas. A first major chamber has a sterile interior thatprovides the manufacturing environment with sealed entry of dropletnozzles while a second minor chamber, atop the first chamber, providesfor another sealed entry of the nozzles in a manner so that both entriescannot be open at the same time, blocking air and particles from entryinto the major chamber. The nozzles deposit layers of structures undercomputer control from software models of the structures while the majorchamber allows for independent X-Y motion and Z motion of the nozzles.Some examples include chambers for printing tissue, living or dead;tissue substrates such as hydroxyapatite, collagen fibers, proteoglycan,and elastin fibers or biological organs or models of organs within asterile yet disposable chamber. Similar examples to those describedabove could be employed with alternative additive manufacturing headtypes such as sputter manufacturing, plasma deposition, fused depositionmodeling (FOM), electron-beam freeform fabrication (EBF3), direct metallaser sintering (OMLS), electron-beam melting (EBM), selective lasermelting (SLM), selective heat sintering (SHS), laminated objectmanufacturing (LOM), stereolithography (SLA), digital light processing(OLP), multi-jet modeling (MJM), etc. Similar examples to thosedescribed above could be employed with combinations of material supplyheads to combine extruded materials with sputtered/sprayed materials inone chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a sterile environment for additivemanufacturing in accordance with the invention wherein a plurality ofnozzles is disposed for entry into the environment.

FIG. 2 shows the apparatus of FIG. 1 with the plurality of nozzlesentrant into the environment.

FIG. 3 is a front partial cut-away view of the apparatus of FIG. 2showing an X-Y motion table connected thereto.

FIGS. 4-6 are front plan views showing successive views of nozzle entryinto valve sealable entry ports of the apparatus of FIG. 1.

FIG. 7 is a front elevational view of the apparatus of FIG. 3 in anadditive manufacturing start position.

FIG. 8 is a front plan view of an enlarged portion of an alternateembodiment of the apparatus of FIG. 3.

FIG. 9 is a plan view of another alternate embodiment of the apparatusof FIG. 3.

DETAILED DESCRIPTION

With reference to FIG. 1, a sterile manufacturing environment 11 is usedfor additive manufacturing. A principal component is a major chamber 15that is closed at its bottom by being attached to the work table 17 thatis fixedly attached to rails 19. The major chamber 15 has a sterileinterior that is closed at its top by top closure 21. Chamber 15 issufficiently large for accommodating a three-dimensional object such asa model of a human skull but is sufficiently small to fit within a 3Dprinter printing chamber. The inside of chamber 15 is sterilized priorto use by any conventional means. The outside of chamber 15 is exposedto the ambient environment and is not sterile. Side straps 23, 25, 27and 29 provide lateral X-Y guiding motion to flexible sidewalls of thechamber 15 to track XY motion of printheads 31 and 33. Note that one orboth of the printheads may operate by extrusion of material. Forpurposes of this patent application, extrusion through a nozzle isconsidered to be printing. Nozzles 41 and 43, associated with printheads31 and 33, respectively, move in the Z direction, shown by arrows Z,under control of a robotic arm, not shown. Nozzles 41 and 43 movethrough a nozzle support fixture 53, particularly nozzle holders 53 and57, in the minor chamber 51 atop the top closure of major chamber 15.The minor chamber 51 is significantly smaller than the major chamber 15.The major chamber must be able to filter air passing through sidewallsof the chamber for expansion and contraction.

The work table 17 is mounted to an XY table in the base of manufacturingequipment in a fixed manner in the orientation best applicable to theitem being printed. Of critical importance is that the baseplate berestricted from independent X,Y motion, apart from the XY table on whichit rests, as well as independent deflection in the Z orientation apartfrom the previously mentioned Z motion in a robot arm during theprinting process to maintain dimensional integrity of the item beingprinted. Alternatively, the XY motion is provided by overhead railsmoving the printheads and no XY table is needed.

Flexible, accordion-style pleated sides of major chamber 15 resemble aChinese lantern or an upside-down origami cone with the lantern or coneattached and sealed to the work table to maintain the sterile barrier.The work table 17 is attached to rails that are part of an XY table thatprovides relative XY motion to the printheads during 3D manufacturing.Sidewalls of the major chamber are moved via clips or elastic straps 23,25, 27 and 29 by coordination with the XY table to keep the sides of themajor chamber 15 from contacting the printed object during themanufacturing process. To facilitate changes in volume of the chamber, apanel or portion of the side or top would be constructed of accordionpleated Tyvek or equivalent breathable sterile barrier. The entireaccordion-style sidewall structure could be constructed of Tyvek orequivalent to provide sufficient breathability. Portions of the sidewallstructure could also be constructed of Mylar or nylon to facilitatevisual inspection of the item being manufactured during processing. Thesidewall structure could be provided with a pealable portion to alloweasy access to the printed item once the sterile barrier can be brokenfor use.

Additionally, quick-detachable and disposable printheads or disposablematerial extrusion heads, described below in FIG. 8, both called“printheads” 41 and 43 are supplied by supply lines 35 and 37, whetherthe supply is liquid to be extruded into the printer or ink-likematerial to be used for supporting the structure under construction.Electronic control lines 45 and 47 provide signals and power to theprintheads in the usual manner. The printheads are joined and sealed tothe top of the minor chamber 51 so that a sealable entry of nozzles intothe major chamber 15 is aligned with a corresponding position for nozzlesealable entry into the minor chamber 51 as explained below.

With reference to FIG. 2, the printheads 31 and 33 are shown to beengaged with nozzle support 53 in minor chamber 51. The nozzles, notshown, have passed through the minor chamber 51 and have entered themajor chamber 15 prior to printing. Engagement of the printheads 31 and33 with the nozzle support is in an airtight manner, for example, by useof a gasket.

In FIG. 3, XY motion to the work table 17 is provided by rails 19sliding in X rail support 39 and driven by a stepper motor or linearactuator. In turn, the X rail support 39 moves in a Y rail support 49 ina manner typical for XY tables. Relative XY motion need not be providedby an XY table below the nozzles but could be provided from above thenozzles, with the work table fixed to a permanent surface. XY tablemotion is coordinated with the XY strap control guide 59 that pulls onside straps 23, 25, 27 and 29 to keep sidewalls of the major chamber outof the way of the printheads moving in the Z direction.

A key feature of the invention is the sequential valving of entry portsfor nozzles moving into the major chamber. With reference to FIG. 4, afirst set of flap valves 61 and 63, associated with the nozzle support53 of minor chamber 51 corresponds to expected positions of the nozzles41 and 43 of the respective printheads 31 and 33. Flap valve 61 has sidepivoting flexing flaps 62 and 64 that are center opening and made ofelastomeric material, such as rubber. A downwardly extending nozzle canreadily open a flex flap with the flap material adhering to the side ofnozzle by its elastomeric property, maintaining a partial seal byfriction contact with the nozzle. This partial seal prevents anysignificant amount of air or particle entry past the flap valve.However, a second set of similar valves 71 and 73 associated with thetop closure of major chamber 15 further presents air and particle entryinto the major chamber 15 as the valves move down into the majorchamber. In FIG. 5, the nozzles 41 and 43 are shown to have penetratedthrough the flap valves 61 and 63 with the flaps 62 and 64 adhering tosidewalls of the nozzles with sliding friction contact. The nozzles areseen approaching the second sealable entry port formed by flap valves 71and 73. In FIG. 6, the nozzles 41 and 43 are shown to have penetratedthrough both sets of flap valves including the first set 61 and 63 thatform a second valve sealable entry port and the second set 71 and 73that form a first valve sealable entry port for the major chamber 15.While two nozzles are shown, it is possible the fewer or more nozzlescould be used.

With reference to FIG. 7, the nozzles 41 and 43 are seen to be fullyentrant through the first and second valve sealable entry ports andextending through the nozzle support 53 into the minor chamber 51 andthe major chamber 15, shown in a collapsed position. Note that when theentry port of the minor chamber is open as in FIG. 5 to allow nozzleentry, the entry port of the major chamber is closed. Then as thenozzles enter, the entry port of the minor chamber closes by the flapvalve sliding against the entrant nozzles. Then the nozzles push openthe entry port of the major valves which is momentarily open until theflaps of the flap valves close by sliding against the entrant nozzles.At no time can both nozzles simultaneously move past both sets of flapvalves since entry past the valves is sequential.

Printing by the nozzles is controlled by a computer, not shown, havingsoftware that guides layer-by-layer formation of biological or otherlamellas. Material used is supplied through supply lines 35 and 37.Ultraviolet or infrared lamps, not shown, may be placed on the undersideof the top closure of the major chamber for accelerating curing of thelamellas. The material dispensed by the nozzles may be material forforming the desired object or one of the nozzles may carry structuralsupport material. Software guides relative X,Y and Z motion of thenozzles from the shown starting position for printing at coordinates 0,0, 0. As each XY layer is printed or otherwise formed, Z motion isincrementally increased and straps 23 and 27 are appropriately pulled bystrap guide control 59 that is coordinated with the XY table to keepsides of the major chamber out of the way of the nozzles 41 and 43. Asstraps are pulled up, sidewalls of the major chamber filter air passingthrough the sidewalls to equalize pressure inside of the major chamber.Chamber material is selected for the desired quality of filtration.Tyvek material removes most particles yet allows air entry.

With reference to FIG. 8, the major chamber 15 has a top closure 21 withtabs 76, 77 and 78 that allow removable joinder of the minor chamber 51to the major chamber 15. The minor chamber 51 encloses the nozzlesupport 53 with nozzle holders 55 and 57 providing mechanical supportfor nozzles 41 and 43. Nozzle 43 is connected to printhead 81. Nozzle 41is connected to heat sink 89 that serves to dissipate heat fromextrusion material tube 85. Extrusion material tube 85 has an internalfilament 87 with an insulative sleeve surrounding the material tube 85carrying the filament that heats material to be extruded through theextrusion printhead 83. The extrusion material tube 85 is fed fromsterile material supply bin 82. Filament 87 is fed from a sterilefilament supply 84 into the material tube 85. Both the sterile materialand the sterile filament are joined at a union 86 that is Y-shaped.Alternatively, the material tube 85 could be manufactured with aninternal filament with the tube extending from the sterile materialsupply bin to the extrusion printhead. The insulative sleeve surroundingthe material tube 85 is external to the union 86. The union supports theoutside of the sleeve while the material tube feeds directly into theunion. The extrusion printhead 83 contains a motor driven gear 93 thatpresses against extrusion material tube 85 which, in turn, bears againstfixed roller 91. Gear 93 maintains heated extruded material in a well 95that forces material into the nozzle 41. Heat sink 89 rejects excessheat by convection to the atmosphere. Printhead 81 is a conventionalinkjet printhead. FIG. 8 shows dual printheads for dispensing ink and abiological extrudeable material in a side-by-side manner.

The filament is a resistive heating element, such as a nichrome wirethat has a thin insulative coating so that when the wire is coiled,adjacent turns will not short. Only a few turns are stored on thesterile filament supply so that a significant amount of heat is not lostin the supply reel 84 that is energized by a DC voltage from powersupply 94. Most of the filament wraps around the material tube 85 tocause sterile material from the material supply bin 82 to flow. Thedistal end of the filament contacts well 95 which has a ground contact96 to complete the heating circuit.

The material tube 85 and the surrounding sleeve, as well as theextrusion printhead 83, but not a connected gear driving servomotor, notshown, as well as heat sink 89 with a material well, and nozzle 41 areall disposable. Disposing of the material contacting members maintainsthe compositional integrity of objects being formed by excluding oldmaterial.

In the alternate embodiment of FIG. 9, XY motion to the nozzles 41 and43 is provided by an X-Y table 66 situated above the nozzles. At thesame time, Z motion is provided by Z motion control 68 situated belowthe work table 17. Nozzles 41 and 43 are associated with twin materialextruders 92 and 94. The nozzles are shown penetrating a first set offlap valves 71 and 73 in the major chamber 15. The nozzles alsopenetrate a second set of flap valves 61 and 63 in the minor chamber 51.The nozzles are depositing material to form an object O on work table 17in a layer-by-layer manner. The object O is within a sterile environmentprotected by the accordion pleated sidewalls of major chamber 15 and thedouble set of entry valves protecting the entry zone for nozzles 41 and43 into major chamber 15. Use of twin extrusion nozzles improvesdeposition times.

When an object is completed, nozzles are withdrawn and discarded. Themajor chamber may be removed in a sealed room to protect themanufactured object and then may also be discarded. Before discardingthe major chamber, the inside sidewalls of the major chamber may betested for bacterial or other contamination in order to certify theintegrity of the manufactured object. When withdrawing the nozzles, theminor chamber may become contaminated with printing residue. The minorchamber is preferably replaced, together with the nozzle support, at thesame time as the major chamber.

What is claimed is:
 1. A method for additive manufacturing in a sterileenvironment comprising: stacking a sterile minor expandable chamber ontop of a major expandable chamber in a vertical arrangement for XYdeposition of lamellas in a sequence for forming an object, the majorexpandable chamber having accordion-pleated, laterally flexiblesidewalls joined to a lower base; providing a double set of entry valvesfor disposable nozzles sequentially entering the sterile expandablechambers, with only one set of entry valves being openable at a time bynozzle entry into the chambers, the nozzles arranged for XY motionrelative to the base for formation of laminar layers of an object; andproviding disposable heated material supply tubes feeding said nozzlesthrough a disposable material extruder connected to a disposable heatexchanger.
 2. The method of claim 1 further defined by heating thedisposable material supply tube with a heated filament.
 3. The method ofclaim 1 further defined by providing vertical major chamber expansion bypulling on said accordion pleated sidewalls of the major chamber forsequentially forming laminar layers of an object.
 4. The method of claim1 further defined by providing XY motion to the base relative tovertical motion of the nozzles.
 5. The method of claim 1 further definedby providing motion in one of the XY directions to the base andproviding motion in the other of the XY directions to the nozzles. 6.The method of claim 1 further defined by providing XY motion to thelaterally flexible sidewalls.
 7. A method for additive manufacturing ina sterile environment comprising: providing a sterile major expandablechamber for XY deposition of lamellas in a sequence for forming anobject; providing a double set of entry valves for disposable nozzlesentering the sterile major expandable chamber; providing disposableheated material supply tubes feeding said nozzles through a disposablematerial extruder connected to a disposable heat exchanger; thendisposing of the nozzles, the heat exchanger, the extruder and thesupply tube after formation of the object.
 8. The method of claim 7further defined by providing expansion of the major chamber by accordionpleated sterile sidewalls.
 9. The method of claim 7 further defined byproviding a minor chamber adjacent to the major chamber with one set ofentry valves opening the minor chamber aligned with another set of entryvalves opening the major chamber.
 10. The method of claim 7 furtherdefined by providing twin material deposition nozzles.
 11. The method ofclaim 7 further defined by providing one material deposition nozzle andone inkjet nozzle.
 12. A method for additive manufacturing in a sterileenvironment, comprising: providing an expandable pleated accordion-type,sealed major chamber having a sterile interior, the major chamberattached along a bottom edge thereof to a worktable and having a lidfastened along a top edge of the major chamber, filtered air capable ofpassing into the chamber as it expands; further providing a minorchamber that is removably fastened to the lid atop the major chamber,the major and minor chambers being separated by a set of flap valvesforming double doors openable only one at a time; further providing atleast one disposable sterile print-head nozzle that enters through theflap valves of the double doors into the major chamber, each print-headnozzle operable to deposit successive layers of material onto theworktable under computer control; dispensing material from the at leastone print-head nozzle while providing relative lateral (x-y) motionbetween the worktable and the nozzle; and successively moving theprint-head nozzle in a relative vertical (z) motion away from thebaseplate while simultaneously expanding the pleated major chamber andfurther dispensing additional layers of material to build up athree-dimensional structure within the sterile environment of thechamber.
 13. The method as in claim 12, further comprising withdrawingthe at least one print-head nozzle from the major and minor chambersthrough the double doors, then removing the major chamber from theworktable in a sealed room to maintain sterile integrity of a finishedthree-dimensional structure.
 14. The method as in claim 12, whereinfiltered air passes into the major chamber, as the major chamberexpands, through fibrous filter material forming sidewalls of thepleated, accordion-type major chamber.
 15. The method as in claim 12,wherein sidewalls of the major chamber are provided with lateral guidingmotion that track relative lateral movement of the print-head nozzle inrelation to the worktable, while simultaneously avoiding contact of thesidewalls with the three-dimensional structure being built uplayer-by-layer within the major chamber.
 16. The method as in claim 15,wherein the lateral guiding motion of the sidewalls is provided by sidestraps attached to the sidewalls.
 17. The method as in claim 12, whereinrelative lateral motion is provided by moving the worktable upon a setof x rail and y rail supports.
 18. The method as in claim 12, whereinrelative vertical motion is provided by raising the at least oneprint-head nozzle.
 19. The method as in claim 12, wherein relativevertical motion is provided by lowering the worktable.
 20. The method asin claim 12, further providing lamps placed on an underside of a topclosure of the major chamber, the lamps accelerating curing of materiallayers dispensed onto the three-dimensional structure being built.